Optical coherence tomography (OCT) is an emerging branch of endoscopy that obtains in vivo cross-sectional images within body cavities and tissues. Forward looking OCT probes observe tissue ahead of the probe so that strictures and sensitive areas can be visualized and avoided. For many clinical applications, e.g., pancreatic cancer identification, the probe should be as narrow as possible. We propose to fabricate and test forward looking probes that maintain high optical resolution but are only about one mm in diameter. The only other forward-looking probe with a comparable diameter is a counter-rotating prism device that uses high speed mechanical motions that may limit its utility. In addition to experts in optics (MF) and Micro Electrical Mechanical Systems, or MEMS (DH), our team includes a board certified veterinarian surgeon with extensive experience in the design and implementation of animal models for human diseases (ML), a well established expert in cancer research (SL), and an experienced endoscopic OCT researcher (JB). In addition our team has two distinguished medical doctors (MR and PF) with extensive clinical and medical research experience with OCT imaging. These doctors recognize an urgent unmet clinical need for a small diameter forward looking OCT probe to image cancers in pancreatico-biliary, breast ductal, gastric, and vascular tissues, and are looking forward to clinical applications of the probe, including diagnostic imaging of pancreatic lesions. This proposal is to construct a compact optical system using the graded index (GRIN) lenses often found in endoscopic probes. We propose a novel optical configuration in which the light travels back and forth through the lens. This simplifies construction while preserving the high optical quality of the image. Most importantly, it minimizes the diameter of the probe. The micro-scanner chip will be developed at LSU and fabricated by a commercial MEMS foundry. One of us (DH) has had considerable experience with similar chips. Assembling the probe is not trivial because the components are so small. However, the group has extensive experience with similar problems and a plan using micro-positioners to hold and align the components is in place. After thorough bench testing, the probes will be used in an existing OCT system at the University of Arizona to image the gastric wall in a rat model. The performance of the probes for in vivo, minimally invasive gastric imaging will be validated by comparing OCT images to light microscopic images of the gastric wall. After the proof-of-concept efforts in this R21, future work will focus on development of a clinical tool for pancreatic cancer imaging. PUBLIC HEALTH RELEVANCE: There is an unmet need for small diameter probes to diagnose cancer by imaging tissue in restricted areas, such as in narrow pancreatic ducts. Endoscopic probes that image with coherent near-infrared light have emerged as a powerful clinical tool. This investigation will maintain the advantages of a forward looking endoscopic probe while reducing the diameter from about 2.4 mm to 1 mm. This new technology will enhance the diagnosis and treatment of a significant patient population.